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Sudhir K Sastry - One of the best experts on this subject based on the ideXlab platform.

  • effects of combination shear stress moderate electric field mef and nisin on kinetics and mechanisms of inactivation of Escherichia Coli K12 and listeria innocua in fresh apple kale blend juice
    Journal of Food Engineering, 2021
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract This work explored the possible synergistic effects of simultaneous application of shear stress-moderate electric field (SS+MEF) in combination with nisin (NS) at ambient temperature on microbial inactivation and quality changes of apple-kale blend juice. In microbiological studies, Escherichia Coli K12 and Listeria innocua were exposed to a) SS+MEF; b) NS; and c) their combinations either simultaneously (SS+MEF+NS) or sequentially (SS+MEF→NS). Quality parameters, including pH, color, antioxidant capacity, and chlorophyll contents of uninoculated juice were also evaluated. Under individual SS+MEF treatment for 10 min, maximum inactivation levels of E. Coli K12 and L. innocua were 5.4 and 5.2 log CFU/mL respectively. NS treatment alone inactivated E Coli K12 and L. innocua by 1.0 and 2.6 log CFU/mL, respectively. Nevertheless, subpopulations of live cells observed by flow cytometry and by plate counts were significantly reduced after both simultaneous and sequential combination treatments, in comparison to individual treatments. SS+MEF+NS treatment produced inactivation levels up to 5-log reductions for both microorganism species within 5 min. The modified Gompertz model best-fitted the inactivation kinetics. SS+MEF+NS treatment for 5 min preserved pH, color, antioxidant capacity and chlorophyll contents of the product, suggesting its potential as a non-thermal preservation technique for fruit and vegetable juices.

  • synergistic effects of shear stress moderate electric field and nisin for the inactivation of Escherichia Coli K12 and listeria innocua in clear apple juice
    Food Control, 2020
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract Rotational shear stress (SS), moderate electric field (MEF), and nisin (NS) treatments were applied to study their effect on inactivation of Gram-negative (Escherichia Coli K12) and Gram-positive (Listeria innocua) bacteria in clear apple juice. We evaluated the combined effects of shear rate (up to 2879 s−1) and MEF with a 60 Hz square-waveform and a duty cycle of 0.50–0.99, at 27 °C; followed by treatment with NS (0–100 IU/ml). The mechanisms of bacterial inactivation were investigated using plate counts and flow cytometry with SYTO-9/propidium iodide (PI) staining. Selected quality attributes (pH, color, and antioxidant activity) of juice samples were also evaluated. It was possible to achieve 5-log cycle reductions of both E. Coli K12 and L. innocua, in samples treated for 5 min with SS at 2879 s−1 and MEF under a duty cycle of 0.99 in combination with NS treatment at 100 IU/ml without significant degradation in quality attributes when compared to the control. Flow cytometry results showed that the mechanism of cellular damage differed for E. Coli K12 and L. innocua. In conclusion, the synergistic effects of the combination of SS+MEF with NS could represent a useful alternative to inactivate target pathogens in foods at temperatures below 30 °C.

  • effect of moderate electric field pretreatment in combination with ozonation on inactivation of Escherichia Coli K12 in intact shell eggs
    Lwt - Food Science and Technology, 2020
    Co-Authors: David Kasler, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract A currently investigated decontamination process for intact shell eggs involves mild water bath heat treatment followed by ozonation. We investigated the effect of a Moderate Electric Field (MEF) applied during water bath pretreatment on the survival of Escherichia Coli K12 (a common Salmonella surrogate for heat processing), inoculated in the albumen. Results showed the addition of an electric field significantly improved (p

  • combined effect of shear stress and moderate electric field on the inactivation of Escherichia Coli K12 in apple juice
    Journal of Food Engineering, 2019
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract The effectiveness of combined shear stress (SS) and moderate electric field (MEF) on the inactivation of Escherichia Coli K12 in apple juice was investigated. Inoculated samples were treated at two temperatures (40 °C and 50 °C) for various times (up to 30 min) by this combined treatment (shear rate: 151.5–2879 s-1; electric field strength: 0–120 V/cm). Bacterial reduction resulting from shear and MEF combination was significantly different (p

Howard Q Zhang - One of the best experts on this subject based on the ideXlab platform.

  • efficacy of supercritical carbon dioxide for nonthermal inactivation of Escherichia Coli K12 in apple cider
    International Journal of Food Microbiology, 2010
    Co-Authors: David J. Geveke, Howard Q Zhang
    Abstract:

    Abstract This study evaluated the efficacy of a supercritical carbon dioxide (SCCO2) system with a gas–liquid porous metal contactor for eliminating Escherichia Coli K12 in apple cider. Pasteurized, preservative-free apple cider was inoculated with E. Coli K12 and processed using the SCCO2 system at CO2 concentrations of 0–10% (wt.%, g CO2/100 g product), outlet temperatures of 34, 38, and 42 °C, a system pressure of 7.6 MPa, and a flow rate of 1 L/min. Increased CO2 concentrations and temperatures significantly (P

  • efficacy of supercritical carbon dioxide for nonthermal inactivation of Escherichia Coli K12 in apple cider
    International Journal of Food Microbiology, 2010
    Co-Authors: Hyungyun Yuk, David J. Geveke, Howard Q Zhang
    Abstract:

    This study evaluated the efficacy of a supercritical carbon dioxide (SCCO(2)) system with a gas-liquid porous metal contactor for eliminating Escherichia Coli K12 in apple cider. Pasteurized, preservative-free apple cider was inoculated with E. Coli K12 and processed using the SCCO(2) system at CO(2) concentrations of 0-10% (wt.%, g CO(2)/100g product), outlet temperatures of 34, 38, and 42 degrees C, a system pressure of 7.6 MPa, and a flow rate of 1L/min. Increased CO(2) concentrations and temperatures significantly (P<0.05) enhanced the bactericidal effect, resulting in a maximum reduction of 7.31 log CFU/mL at 8% CO(2) and 42 degrees C. A response surface model indicated that minimum CO(2) concentrations of 9.9% at 34 degrees C, 7.4% at 38 degrees C, and 5.4% at 42 degrees C are needed to achieve a 5-log reduction of E. Coli K12 in apple cider. SEM observations showed morphological changes in the cell envelope after SCCO(2) processing. At a processing condition of 8% and 38 degrees C, the reduction of E. Coli was 6.03 log and the sublethal injury of the survivors was 84%. The regrowth or survival of E. Coli in SCCO(2) processed apple cider was not observed during storage for 28 days at 4, 8, and 20 degrees C. Thus this study showed the potential of SCCO(2) processing with a gas-liquid porous metal contactor for the nonthermal pasteurization of apple cider.

  • comparison of aluminum thermal death time disks with a pilot scale pasteurizer on the thermal inactivation of Escherichia Coli K12 in apple cider
    Food Control, 2009
    Co-Authors: Hyungyun Yuk, Howard Q Zhang, David J. Geveke, Tony Z. Jin
    Abstract:

    Abstract This study was conducted to compare thermal inactivation kinetics obtained using a pilot-scale pasteurizer and a bench-scale processing system. Pilot-scale pasteurizers are useful for product development, but comparisons on thermal inactivation kinetics with smaller scale systems are lacking. Using an Armfield pilot-scale pasteurizer and aluminum thermal-death-time (TDT) disks, the D-values and z-values of Escherichia Coli K12 in apple cider were determined in the temperature range of 54–62 °C. Come-up times to 58 °C were also measured and were 35 and 61 s for the TDT disks and pasteurizer, respectively. The D-values from the TDT disks were 9.66, 4.01, 1.44 and 0.44 min at temperatures of 54, 56, 58, and 60 °C, respectively. The D-values from the pasteurizer were 3.48, 1.22, 0.10 and 0.05 min at temperatures of 56, 58, 60, and 62 °C, respectively. The z-values from the TDT disks and the pasteurizer were 4.68 and 3.60 °C, respectively. There was no significant (P > 0.05) difference in the D-values of the TDT disks and pasteurizer at 56 and 58 °C, while there was a significant (P

  • thermal resistance of salmonella enteritidis and Escherichia Coli K12 in liquid egg determined by thermal death time disks
    Journal of Food Engineering, 2008
    Co-Authors: Howard Q Zhang, Glenn Boyd, Juming Tang
    Abstract:

    Abstract A thermal-death-time (TDT) disk was designed to evaluate microbiological inactivation kinetics by heat. A first order inactivation kinetic model is described by the D value and the z value. These kinetic data are critical in the design, operation and regulation of thermal pasteurization. D and z values of Salmonella enteritidis strain 13076 and Escherichia Coli K12 in liquid whole egg and liquid egg white were determined over the temperature range from 52 to 60 °C. In liquid whole egg, D 54 , D 56 , D 58 and D 60 values of S. enteritidis strain 13076 were 5.70, 0.82, 0.27 and 0.17 min, respectively, and D 54 , D 56 , D 58 and D 60 values of E. Coli K12 were 9.10, 1.41, 0.67 and 0.22 min, respectively. In liquid egg white, D 52 , D 54 , D 56 and D 58 values of S. enteritidis strain 13076 were 6.12, 1.51, 0.42 and 0.19 min, respectively, and D 52 , D 54 , D 56 and D 58 values of E. Coli K12 were 10.18, 1.82, 0.78 and 0.28 min, respectively. The z values for S. enteritidis strain 13076 and E. Coli K12 ranged from 3.95 to 4.03 °C. The results showed that D values of S. enteritidis strain 13076 and E. Coli K12 in liquid whole egg were higher than those in liquid egg white. E. Coli K12 exhibited similar kinetic behavior, but higher thermal resistance than S. enteritidis strain 13076 in both liquid egg white and liquid whole egg. This study demonstrated that non-pathogenic E. Coli K12 may serve as a surrogate for pathogenic S. enteritidis in liquid egg in the validation of a thermal pasteurization.

Menachem Elimelech - One of the best experts on this subject based on the ideXlab platform.

  • role of type 1 fimbriae and mannose in the development of Escherichia Coli K12 biofilm from initial cell adhesion to biofilm formation
    Biofouling, 2009
    Co-Authors: Debora F Rodrigues, Menachem Elimelech
    Abstract:

    The influence of type 1 fimbriae, mannose-sensitive structures, on biofilm development and maturation has been examined by the use of three isogenic Escherichia Coli K12 strains: wild type, fimbriated, and non-fimbriated. Experiments with the three strains were done in minimal medium or Luria–Bertani broth supplemented with different concentrations of d-mannose. The investigation consisted of: (1) characterizing the bacterial surface of the three strains with respect to hydrophilicity and surface charge, (2) investigating the effect of type 1 fimbriae on bacterial adhesion rate and reversibility of initial adhesion on glass surfaces, and (3) verifying the role of type 1 fimbriae and exopolysaccharides (EPS) in biofilm maturation. The results suggest that type 1 fimbriae are not required for the initial bacterial adhesion on glass surfaces as the non-fimbriated cells had higher adhesion rates and irreversible deposition. Type 1 fimbriae, however, are critical for subsequent biofilm development. It was hypo...

  • role of cell surface lipopolysaccharides in Escherichia Coli K12 adhesion and transport
    Langmuir, 2004
    Co-Authors: Sharon L Walker, Jeremy A Redman, Menachem Elimelech
    Abstract:

    The influence of bacterial surface lipopolysaccharides (LPS) on cell transport and adhesion has been examined by use of three mutants of Escherichia Coli K12 with well-characterized LPS of different lengths and molecular composition. Two experimental techniques, a packed-bed column and a radial stagnation point flow system, were employed to investigate bacterial adhesion kinetics onto quartz surfaces over a wide range of solution ionic strengths. Although the two systems capture distinct deposition (adhesion) mechanisms because of their different hydrodynamics, similar deposition kinetics trends were observed for each bacterial strain. Bacterial deposition rates were directly related to the electrostatic double layer interaction between the bacteria and quartz surfaces, in qualitative agreement with classic Derjaguin−Landau−Verwey−Overbeek (DLVO) theory. However, DLVO theory does not fully explain the deposition behavior for the bacterial strain with the lengthy, uncharged O-antigen portion of the LPS. Ne...

  • role of cell surface lipopolysaccharides in Escherichia Coli K12 adhesion and transport
    Langmuir, 2004
    Co-Authors: Sharon L Walker, Jeremy A Redman, Menachem Elimelech
    Abstract:

    The influence of bacterial surface lipopolysaccharides (LPS) on cell transport and adhesion has been examined by use of three mutants of Escherichia Coli K12 with well-characterized LPS of different lengths and molecular composition. Two experimental techniques, a packed-bed column and a radial stagnation point flow system, were employed to investigate bacterial adhesion kinetics onto quartz surfaces over a wide range of solution ionic strengths. Although the two systems capture distinct deposition (adhesion) mechanisms because of their different hydrodynamics, similar deposition kinetics trends were observed for each bacterial strain. Bacterial deposition rates were directly related to the electrostatic double layer interaction between the bacteria and quartz surfaces, in qualitative agreement with classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. However, DLVO theory does not fully explain the deposition behavior for the bacterial strain with the lengthy, uncharged O-antigen portion of the LPS. Neither the length nor the charge characteristics of the LPS molecule directly correlated to deposition kinetics, suggesting a complex combination of cell surface charge heterogeneity and LPS composition controls the bacterial adhesive characteristics. It is further suggested that bacterial deposition behavior is determined by the combined influence of DLVO interactions, LPS-associated chemical interactions, and the hydrodynamics of the deposition system.

Lene Jespersen - One of the best experts on this subject based on the ideXlab platform.

  • attachment behaviour of Escherichia Coli K12 and salmonella typhimurium p6 on food contact surfaces for food transportation
    Food Microbiology, 2012
    Co-Authors: Stephen Abban, Mogens Jakobsen, Lene Jespersen
    Abstract:

    Abstract The role of cargo container lining materials aluminium, a fibre reinforced plastic (FRP) and stainless steel in bacterial cross contamination during transport was assessed. For this, attachment and detachment of Escherichia Coli K12 and Salmonella Typhimurium P6 on the three surfaces in the absence or presence of residues were evaluated. Observations were correlated with water contact angles of the materials (hydrophobicity) and roughness profile (Ra). Attachment of the organisms was negatively correlated to the hydrophobicity of the three materials with r = −0.869 and −0.861 for E. Coli K12 and S. Typhimurium P6 respectively. Correlation with roughness average was poor; r = −0.425 and −0.413 respectively for E. Coli K12 and S. Typhimurium P6. Presence of residue caused significant reduction (p

  • attachment behaviour of Escherichia Coli K12 and salmonella typhimurium p6 on food contact surfaces for food transportation
    Food Microbiology, 2012
    Co-Authors: Stephen Abban, Mogens Jakobsen, Lene Jespersen
    Abstract:

    Abstract The role of cargo container lining materials aluminium, a fibre reinforced plastic (FRP) and stainless steel in bacterial cross contamination during transport was assessed. For this, attachment and detachment of Escherichia Coli K12 and Salmonella Typhimurium P6 on the three surfaces in the absence or presence of residues were evaluated. Observations were correlated with water contact angles of the materials (hydrophobicity) and roughness profile (Ra). Attachment of the organisms was negatively correlated to the hydrophobicity of the three materials with r = −0.869 and −0.861 for E. Coli K12 and S. Typhimurium P6 respectively. Correlation with roughness average was poor; r = −0.425 and −0.413 respectively for E. Coli K12 and S. Typhimurium P6. Presence of residue caused significant reduction (p

Jin Hong Mok - One of the best experts on this subject based on the ideXlab platform.

  • effects of combination shear stress moderate electric field mef and nisin on kinetics and mechanisms of inactivation of Escherichia Coli K12 and listeria innocua in fresh apple kale blend juice
    Journal of Food Engineering, 2021
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract This work explored the possible synergistic effects of simultaneous application of shear stress-moderate electric field (SS+MEF) in combination with nisin (NS) at ambient temperature on microbial inactivation and quality changes of apple-kale blend juice. In microbiological studies, Escherichia Coli K12 and Listeria innocua were exposed to a) SS+MEF; b) NS; and c) their combinations either simultaneously (SS+MEF+NS) or sequentially (SS+MEF→NS). Quality parameters, including pH, color, antioxidant capacity, and chlorophyll contents of uninoculated juice were also evaluated. Under individual SS+MEF treatment for 10 min, maximum inactivation levels of E. Coli K12 and L. innocua were 5.4 and 5.2 log CFU/mL respectively. NS treatment alone inactivated E Coli K12 and L. innocua by 1.0 and 2.6 log CFU/mL, respectively. Nevertheless, subpopulations of live cells observed by flow cytometry and by plate counts were significantly reduced after both simultaneous and sequential combination treatments, in comparison to individual treatments. SS+MEF+NS treatment produced inactivation levels up to 5-log reductions for both microorganism species within 5 min. The modified Gompertz model best-fitted the inactivation kinetics. SS+MEF+NS treatment for 5 min preserved pH, color, antioxidant capacity and chlorophyll contents of the product, suggesting its potential as a non-thermal preservation technique for fruit and vegetable juices.

  • synergistic effects of shear stress moderate electric field and nisin for the inactivation of Escherichia Coli K12 and listeria innocua in clear apple juice
    Food Control, 2020
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract Rotational shear stress (SS), moderate electric field (MEF), and nisin (NS) treatments were applied to study their effect on inactivation of Gram-negative (Escherichia Coli K12) and Gram-positive (Listeria innocua) bacteria in clear apple juice. We evaluated the combined effects of shear rate (up to 2879 s−1) and MEF with a 60 Hz square-waveform and a duty cycle of 0.50–0.99, at 27 °C; followed by treatment with NS (0–100 IU/ml). The mechanisms of bacterial inactivation were investigated using plate counts and flow cytometry with SYTO-9/propidium iodide (PI) staining. Selected quality attributes (pH, color, and antioxidant activity) of juice samples were also evaluated. It was possible to achieve 5-log cycle reductions of both E. Coli K12 and L. innocua, in samples treated for 5 min with SS at 2879 s−1 and MEF under a duty cycle of 0.99 in combination with NS treatment at 100 IU/ml without significant degradation in quality attributes when compared to the control. Flow cytometry results showed that the mechanism of cellular damage differed for E. Coli K12 and L. innocua. In conclusion, the synergistic effects of the combination of SS+MEF with NS could represent a useful alternative to inactivate target pathogens in foods at temperatures below 30 °C.

  • combined effect of shear stress and moderate electric field on the inactivation of Escherichia Coli K12 in apple juice
    Journal of Food Engineering, 2019
    Co-Authors: Jin Hong Mok, Taras Pyatkovskyy, Ahmed E Yousef, Sudhir K Sastry
    Abstract:

    Abstract The effectiveness of combined shear stress (SS) and moderate electric field (MEF) on the inactivation of Escherichia Coli K12 in apple juice was investigated. Inoculated samples were treated at two temperatures (40 °C and 50 °C) for various times (up to 30 min) by this combined treatment (shear rate: 151.5–2879 s-1; electric field strength: 0–120 V/cm). Bacterial reduction resulting from shear and MEF combination was significantly different (p